Creating an Eco‐Friendly Building Coating with Smart Subambient Radiative Cooling

TLDR

Subambient daytime radiative cooling offers a promising electricity‑ and cryogen‑free pathway for global energy efficiency, yet current systems require stringent, costly, and non‑eco‑friendly surface designs to selectively emit thermal radiation to outer space while maximizing solar reflectance. The study aims to develop a generic method to upgrade conventional building‑coating materials with a self‑adaptive subambient daytime radiative cooling effect. This method achieves the effect by combining particle scattering, sunlight‑excited fluorescence, and mid‑infrared broadband radiation. The approach theoretically eliminates the need for resonant microstructures and noble‑metal mirrors, enhances daytime cooling while suppressing nighttime overcooling, and experimentally achieves up to 6 °C below ambient (84.2 W m⁻² cooling power) under direct sunlight, indicating promise for large‑scale building applications.

Abstract

Subambient daytime radiative cooling (SDRC) provides a promising electricity- and cryogen-free pathway for global energy-efficiency. However, current SDRC systems require stringent surface designs, which are neither cost-effective nor eco-friendly, to selectively emit thermal radiation to outer space and simultaneously maximize solar reflectance. Here, a generic method is developed to upgrade the conventional building-coating materials with a peculiar self-adaptive SDRC effect through combining particle scattering, sunlight-excited fluorescence, and mid-infrared broadband radiation. It is also theoretically proved that heat exchange with the sky can eliminate the use of resonant microstructures and noble metal mirrors in conventional SDRC, and also leads to enhanced daytime cooling yet suppressed nighttime overcooling. When exposed to direct sunlight, the upgraded coating over an aluminum plate can achieve 6 °C (7 °C on a scale-model building) below the ambient temperature under a solar intensity of 744 W m-2 (850 W m-2 ), yielding a cooling power of 84.2 W m-2 . The results pave the way for practical large-scale applications of high-performance SDRC for human thermal comfort in buildings.